Alice, a young woman grieving the death of her mother, finds a friend in the older Ida, but her new friend seems to have sinister intentions.

Based on true events, the film follows Mathilde Cordier, a young detective from the Criminal Investigation Division with a history of abuse, is laid off as an intervention goes awry. Following the disappearance of a young girl, Mathilde, outside the law, will conduct her own investigation and follow the trail of a man named François Renard. A man with a troubled and violent past who claims to have settled down. As she sinks into a spiral of darkness, Mathilde faces the most monstrous aspects of humanity.